In a flip chip semiconductor device, a semiconductor die is mounted directly onto a substrate, board, or carrier (hereinafter substrate). Electrical connection is achieved through conductive bumps formed on the surface of the semiconductor die. The conductive bumps are aligned with conductive patterns on the substrate. A non-conductive filler material is applied to the open spaces between the surface of the semiconductor die and the substrate. The non-conductive filler material is used to protect the interface between the conductive bumps on the surface of the semiconductor die and the conductive patterns on the substrate from moisture, contaminants, and other environmental hazards. The non-conductive filler material further aids in securing the semiconductor die to the substrate.
A protective covering is then formed over the semiconductor die, the non-conductive filler material, and the substrate. The protective covering may be an encapsulant. Alternatively, a lid may be positioned over the semiconductor die and attached to the substrate. In some situations, the lid is used not only as a protective covering but also as a way to dissipate heat from the semiconductor die. The lid is generally formed of a metallic material. However, ceramic material may be used as well.
The lid is attached to the semiconductor die and the substrate. The material used to attach the lid to the semiconductor die is different from the material used to attach the lid to the substrate. In general, a thermal interface material (TIM) such as silicone loaded with high thermal conductivity material is placed between the semiconductor die to the lid. This type of material aids in the dissipation of heat from the semiconductor die to the lid. An adhesive material is generally used to attach the lid to the substrate.
A problem with lidded semiconductor devices is that thermal interface material (TIM) degradation may occur. The degradation is due to excessive mechanical strains induced within the TIM when the semiconductor device undergoes severe temperature excursions. These temperature excursions may occur during processing steps subsequent to lid attachment such as moisture resistance testing (MRT), or in the field, such as those produced during power cycling. Semiconductor devices warp in response to a change in temperature and differences in thermal expansion coefficient in lid, die and substrate. Excessive warpage causes failure between the semiconductor die and TIM interface and the lid and the TIM interface.
Therefore, a need exists to provide a device and method to overcome the above problems. The device and method would reduce the adhesive failure between the semiconductor die and TIM interfaces and the lid and the TIM interfaces due to lid warpage.